This invention is intended for use in the hydrocarbon, geothermal and mining resources industries, and generally relates to methods and apparatus that are utilized for modifying subsurface resource formation permeability and providing means for the movement of formation fluids, materials and/or other fluids and/or other materials within and/or through the modified permeability within a resource bearing formation. More particularly, the invention relates to such methods and apparatuses that use the energy released by high power Magnetohydrodynamic Plasma Spark (MPS) discharges to alter the productivity of a resource bearing formation. The energy released from the high power MPS discharges generates nonlinear, directed, wide band and elastic controlled periodic oscillations that affect the resource bearing formation material and fluids in varying but complimentary ways to act in altering productivity of said resource bearing formation.
The invention further relates to modifying the productive capacity of resource bearing formations that have been drilled with production and/or injection wellbores into resource bearing formations that are conventionally classified or commonly known as new, mature, and/or depleted resource bearing formations. Said resource bearing formations may be either on-shore or off-shore. The wellbores drilled to access the resource bearing formations may be drilled as vertical, directional, horizontal or any combination thereof. The invention utilizes high power MPS discharge produced oscillations, generated within said wellbores, to modify the permeability of said resource bearing formations and thereby modify the fluidization, viscosity, mobility and/or other physical characteristics of resource bearing formation fluids and/or materials to enhance production of chemicals, chemical compounds (such as hydrocarbons), heat energy and/or resource materials.
The invention may find useful applications in environmentally positive related types of processes, such as increasing the productive capacity of all types of geothermal energy bearing formations, carbon dioxide injectable formations, waste disposal injectable formations and formation for the conservation of various materials.
An exemplary description of the method and apparatus of the present invention will be described in reference to chemical compound (hydrocarbon) resource production, and more specifically, oil production. It is understood that the described method and apparatus can be utilized and/or modified to be utilized to produce almost any subsurface fluid and/or material that can be fluidized as a producible resource such as water, hydrocarbons, geothermal heat energy, diamonds, potash, and like resources.
Oil production operators attempt to produce the maximum volume of their oil resource reserves within a hydrocarbon bearing formation at the lowest cost during the formations primary production phase. A production wellbore's primary production phase is defined as the phase during which the in situ formation pressure drive mechanism will force the hydrocarbon to a wellbore. Once the formations production drive mechanism can no longer economically force the hydrocarbons to the wellbore, more expensive and complicated secondary and tertiary technology methods are employed if additional hydrocarbons are to be produced into a wellbore. A typical cause for resource reservoirs to lose production related drive pressures is the resource formation permeability becomes partially or fully plugged over time, thereby isolating the any production drive pressure remaining from the wellbore. As numerous oil bearing reservoirs have become pressure depleted worldwide, advanced methods of enhanced production of the oil in place needs to be developed to extract economically significant amounts of technically non-producible hydrocarbons left in the reservoirs being produced by conventional primary, secondary, and tertiary means.
As is commonly known within the oil and gas industry, the historical average level of primary oil production from typical wells drilled into conventionally completed oil bearing formations has been approximately 30% and <10% from wells drilled into unconventional oil bearing formation wells.
The primary causes for the low percentage level of oil production is the loss of useable drive pressure through pressure depletion or produced particle and/or chemical precipitate clogging or completely plugging the productive formation's permeability. The result of undesirable drilling or completion processes and/or the cumulative effects of reservoir production material swelling, movement and/or the chemical generation of precipitous particle accumulation of materials within the oil bearing formation tend to reduce or totally inhibit the oil production process. Specifically, particle movement and/or precipitate clogging of the near-wellbore area permeability, in particular, is one of the most common causes for the reduction in oil production over time.
In additional to conventional mechanical completion processes, numerous methods and apparatus for enhancing hydrocarbon production have been researched and applied with varying degrees of success. Chemical, microbiological, thermal-gas-chemical and similar methods generally rely on using various agent-assisted processes, including: injection of steam, foam surfactants and/or air, the latter being accompanied by low-temperature or high-temperature oxidation, in situ formation of emulsions, directed asphaltene precipitation, chemical thermal desorption, selective chemical reactions in light oil reservoirs and heavy oil deposits, chemical agent assisted alterations of phase properties, including wettability and interfacial tension, and alkaline-surfactant polymer flooding are illustrative.
Limited and temporary remedially enhanced oil production has been achieved through stimulating the formation, formation fluids and/or wellbore casing perforations with hydro-mechanical and/or electrically generated wellbore fluid oscillation effects. Movement of near field permeability plugging and/or blockage material, resulting from cumulative production material or chemical deposits, and increased wellbore oil inflows have been achieved by means of agent-free oscillation stimulation apparatuses. These oscillation producing apparatuses include mechanical (hydro-mechanical) and electric (electromagnetic, ultrasonic, acoustic, and electrohydraulic) emitter devices, as well as combinations thereof.
Oscillation producing apparatus utilize hydrodynamic oscillation emitters such is typical of that taught in U.S. Patent Application Publication No. 2003/0201101 authored by Kostov et al and U.S. Pat. No. 4,060,128 issued to Wallace, or electric plasma oscillation emitters such as is typical of that taught in U.S. Pat. No. 4,345,650 issued to Wesley et al and U.S. Pat. No. 4,074,758 issued to Scott. Both type of oscillation emitters are typically deployed within a wellbore, positioned at depth and operated at a producing formation interval. These tools operate to emit oscillatory vibrations into the wellbore ambient fluid and subsequently into the productive formation through wellbore casing perforations or through an open-hole section of the wellbore. The wellbore fluid, typically a liquid, provides a good hydrodynamic coupling media to transmit the oscillatory vibrations from the emitter into the geological formation.
It is commonly known, that based on energy density, the potential to develop the highest power oscillations is greatest using electric plasma oscillation emitters. These electric plasma oscillation emitters are typically deployed into, positioned, moved from point to point within the wellbore and supplied with power by means of a spooled wire line system situated at the surface.
The typically completed wellbore diameters are a nominal 10.2 cm or less for cased holes or a nominal 15.24 cm for open hole completions. These are the most common wellbore diameters due to established economics. These wellbore diameter constraints severely limit the physical size of any mechanical and/or electrical oscillation emitter systems that can be deployed downhole.
The universally small completed wellbore diametrical constraint has limited the ability to develop high energy density pulsed power storage means to operate electrical oscillation emitters that are deployed downhole for use. Specifically, the wellbore diametrical constraint typically limits the practical downhole energy storage capacity of the prior art electrical oscillator systems to ≤2.0 kJ. While a few of the prior art teachings discuss or infer the use of larger downhole energy storage means, none of them describe the specifications able to achieve energy storage capacity above 2.0 kJ. Further, only recently have plasma oscillation emitters become commercially available and they operate at the ≤1.5 kJ energy level as advertised by Blue Spark Energy, Inc.'s and Propell Technologies Group's internet presentations.
At low energy storage levels (≤2.0 kJ), the prior art electric plasma oscillation emitters are practically limited to generating only minor near field formation modifications and/or low energy production stimulation. The prior art plasma oscillation apparatus have been unable to achieve sustained economically significant production enhancement due to their limitation of low energy density coupled with the complexities of reliably operating intricate mechanical and/or electro-mechanical systems within the deployed tool that must be operated in a harsh downhole environment.
Exemplary of prior art electric plasma oscillators is U.S. Patent Application Publication No. 2014/0027110 A1 invented by Ageev et al which discloses an electric plasma emitting oscillation apparatus and method to provide a wellbore centric enhancement of oil production by means of the remediation of the near-field filtration properties of the productive formation. The method comprises the production of wellbore centric plasma generated shock and hydrodynamic waves travelling radially within an ambient wellbore liquid as the result of generating a brief, but powerful plasma bubble. The plasma bubble is generated by the explosive electrical shorting of a calibrated metal wire filament located between two submerged electrodes. Ageev's teachings focus on the explosive generation of a plasma bubble that instantaneously emits a shock wave oscillation with hypersonic acoustical velocity and a slower velocity hydrodynamic pulse wave. The purpose of operating this emitter tool is to utilize the shock wave and hydrodynamic oscillations to dislodge production related blockages from within the casing perforations and/or the near field formation permeability and the subsequent inflow movement of the blockage material into the wellbore. The action of dislodging and removal of the blockage material provides a temporary increase in the productive inflow of formation fluids into the wellbore. If successful in stimulating the formation, the increased inflows are temporary, lasting from several days to several months. In operation, the described system deploys the downhole plasma emitting tool system into the wellbore by means of a surfaced located truck mounted spooled wire line system. The surfaced located conventional power supply system within the wire line truck provides an electrical current to charge to a downhole capacitor based pulsed power system transmitted through conductors within the deployment wire line cable. The downhole plasma emitter tool system employs several electrical and/or electronic sub-systems for charging, energy storage, and controlling the firing and charging sequences of the plasma emitter tool system. The downhole capacitor based energy storage, electronic control and firing circuits, circuit electrodes, and the wire filament replacement system are all contained within the downhole emitter tool system that is wire line deployed to a target formation depth within the wellbore. The various prior art teachings of wire line deployment of the plasma emitter systems along with its energy storage sub-system into the wellbore limits the energy storage capacity, the operable temperature, and the deployment angle capabilities of the apparatus. Due to the size limitations of the small plasma emitter's capacitor energy storage sub-system, the energy and power levels and wave forms of the shock waves that this type of plasma emitter can generate is severely limited in its range. The plasma emitted shock wave power and wave form are critical to effectively generating formation modifications such as formation filtration and fracturing as describe by Ageev. The low energy storage capacity causes critical tradeoffs between generating relatively high power, high frequency or relatively low power, low frequency shock waves which severely limits the range and magnitude of the formation effects and the radial distance the shock waves can be effective in modifying the productive formation properties. The cumulative effect of the low energy capabilities of the apparatus as taught by Ageev, is that it is only effective in generating near-field filtration effects and has very little effectiveness, if any, in fracturing the formation. Further, and again, due to the low energy density limits on power and wave forms, this category of apparatus is only effective in generating very near-field formation filtration enhancements that are temporary in nature. One operational problem identified with these types of plasma emitter systems is that the sacrificial metal conductor filament as taught by Ageev, suffers high energy losses, typically 15 to 50% of the stored energy at the stage of conductor heating due to melting, evaporation, and high optical radiation losses. These stated energy losses drastically decrease the acoustic and hydrodynamic shock wave intensity due to the relatively smaller volume plasma. Another operational problem occurs with this type of plasma emitter due to the need for continuously replacing the sacrificial metal wire filament after each plasma generation sequence. The filament replacement requires a complex electro-mechanical filament replacement sub-system means. Such electro-mechanical means generally do not operate reliably under the typically harsh downhole environment (high pressure, high temperature, and corrosive fluids) coupled with repeated high power electromagnetic, acoustic and/or hydrodynamic shock generating events. Further, these mechanical and/or electro-mechanical filament replacement systems typically lack reliability due to the surface rupture or sticking of the filaments at the point where they come into contact with the current conducting parts before, during and/or after the plasma generation. Still further, the materials of the current conducting parts undergo substantial material ablation due to the filament related dynamic vaporization and erosion processes as the plasma is formed. The described system is therefore operationally limited to near-field remedial filtration treatment of the formation due to energy limitations; can operate only in relatively low bottom-hole temperatures due to temperature-limited electronic equipment failures, and can only operate in non-horizontal wellbores due to lack of the ability to push the tool horizontally to the bottom of the hole without third party equipment. The described equipment and operational related short comings eliminate many thousands of existing wellbores and hundreds of thousands of potential new wellbores from applying the described electrical plasma oscillation emitter as taught by Ageev.
In additional to the Ageev teachings, the following list of prior art references teaches apparatus and methods similar to that taught by Ageev in that they also attempt to modify the productive formation permeability (filtration) and/or mobilize oil inflow and/or mobilize oil radially towards adjacent wellbores utilizing low energy storage capacity for producing pulsed plasma discharges. The prior art exclusively teaches the use of downhole capacitors to provide pulsed power to the electric plasma oscillation emitter systems. These additional references provide teachings, insights and/or support for the descriptions of the faults and shortcomings of the low energy density electric plasma oscillators as discussed concerning the Ageev patent application. These additional references are as follows:                a) U.S. Pat. No. 4,343,356 issued to Riggs et al        b) U.S. Pat. No. 4,345,650 issued to Wesley et al        c) U.S. Pat. No. 4,667,738 issued to Codina        d) U.S. Pat. No. 4,997,044 issued to Stack        e) U.S. Pat. No. 5,004,050 issued to Sizonenko et al        f) U.S. Pat. No. 6,227,293 issued to Huffman et al        g) U.S. Pat. No. 8,220,537 issued to Leon et al        
Exemplary of another prior art electric plasma oscillator is U.S. Patent Application Publication No. 2014/0008073 A1 invented by Rey-Bethbeder et al which discloses a typical wire line deployed downhole electric plasma oscillation emitting apparatus and method to provide of enhancement of hydrocarbon production by means of the wellbore centric fracturing of the near-field productive formation to an approximate 30 m radius along the axis of a horizontal wellbore. Interestingly, one of the rudiments of this teaching is the integrated use of electric fracturing before, during or after applying conventional static hydraulic fracturing. Bethbeder teaches the use of up to 2.0 MJ of energy to operate the plasma emitter, but fails to teach a means to achieve the downhole storage of the 2.0 MJ of energy within the downhole plasma emitter described. The typical wellbore diameter constraints of either vertical or horizontal wellbores renders a downhole capacitor system storage of 2.0 MJ of energy unfeasible as is discussed concerning the Ageev patent application and explanations found in the additional downhole plasma emitter prior art references. Further it is common knowledge that it would be unworkable to supply an electrical energy surge of 2.0 MJ of energy from a surface location through a long wire line due to the physical limitations of current wire line insulation and temperature related strength technology for typical oilfield wellbore deployable wire lines. Still further, Bethbeder was silent about the prohibited cost associated with drilling and completing a significantly larger diameter wellbore that would be required to practically accommodate the diametrical dimensions of a downhole tool necessary to include a capacitor sub-system capable of storing up to 2.0 MJ of energy. The energy density of capacitors has been the key obstacle in deploying increased capacitor energy storage systems within downhole plasma emitter tools based on wire line deployment. Additionally, Bethbeder's teachings infer being able to fracture a formation by means of a plasma discharge at the calculated energy compression level 0.032 MJ/μs at a corresponding power compression of 0.032 MW/μs for approximately 10,000 μs (0.01 seconds) at an initial shock wave frequency of approximately 100 Hz in an omni directional manner. The total energy per plasma shot described by Bethbeder would be approximately 0.32 GJ/plasma discharge shot which translates to a power of approximately 1.34 tons of TNT dynamite. Bethbeder teaches that this level of power could generate high density formation fracturing to a nominal 30 m radius along a horizontal wellbore. Drawing from legacy wellbore “shooting” field experiments with chemical explosives, and more specifically the “Gasbuggy Project”, the first underground nuclear explosion field test associated with the U. S. Government Plowshare peaceful nuclear development program, in which a 120 TJ (29 kt of TNT) explosion only managed to generate a 24 m diameter by 102 m rubblized geological formation chimney. Therefore, as a practical matter, even at the inferred maximum energy compression of 0.32 GJ/plasma (1.3 t of TNT) discharge, as taught by Bethbeder, the described apparatus would not be able to achieve his stated 30 m radial zone of rubblized formation along the axis of a horizontal wellbore no matter how many repetitive discharges were to be used. The levels of energy taught by Bethbeder are inconsistent with the significant body of public domain information available to compare energy levels in generating near-field wellbore fracturing as described by Bethbeder. Bethbeder also teaches the use of electric fracturing in conjunction with static hydraulic fracturing, before, during or after static hydraulic fracturing. It is common knowledge that wellbore centric explosively generated (chemical and/or electric) compressive shock waves radially compact the formation until a radially stratified threshold density has been achieved within the near-field geological formation. At this point the shock wave is materially reflected back towards the source of the shock waves and travels through the formation material as a tension stress force thereby failing the formation material in its weakest stress mode. The effect is one of rubblizing the formation material interior to the point of shock wave reflection. This effect is known as the development of a radial formation densification that forms a Radial Stress Cage (RSC) that surrounds the wellbore as a result of wellbore centric explosive events. The generally instantaneous formation radially stratified densification that takes place during the formation of the RSC would force any existing or developing static hydraulic macro-fractures to instantaneously collapse and close due to formation dilatation, densification and radial compaction resulting from the electric fracturing process. The RSC within the formation would prevent any static hydraulic generated macro fracture enhancement. Further, if the static hydraulic fracturing was attempted after the electric fracturing, the static hydraulic fracturing would be ineffective in generating the intended long radial macro fractures as described by Bethbeder. This is due to the RSC generated by the electric fracturing would act as a barrier to static hydraulic fracturing pressure as the RSC would have the effect of elevating the necessary static fracturing hydraulic pressure, necessary to fracture through the RSC area of formation densification, to an unworkable hydraulic pressure level for the safe operation of either the hydraulic fracturing equipment or the wellbore equipment. Further, the static fracture pressure would be spread over a significantly larger radial surface area due path-of-least-resistance static hydraulic pressure spreading within the electrical fracture rubblized zone along the wellbore axis thereby requiring significantly increased volumes of fracturing fluids. Still further, any desired control of the placement of static macro fractures would be lost under these circumstances. Thus the teachings of Bethbeder a) fail to describe a practical means of providing up to 2.0 MJ downhole energy storage; b) fails to describe sufficiency of downhole energy storage to be able to conduct near-field electrical formation fracturing results as described by Bethbeder; c) joins the categorical ranks of low energy pulsed plasma emitter oscillation means and d) describes an impractical and ineffective method of attempting to combine the use of electrical and static hydraulic fracturing.
The prior art has described low energy pulsed plasma emitter oscillator systems and methods. These low energy pulsed plasma emitter oscillator systems appeared to have great promise but have either been impractical to economically deploy or relegated to economically insignificant niche operations due to low energy levels available. None of the prior art has provided an entirely workable or an economically significant means of generating formation modifications and/or resource mobilization within a resource bearing formation through the use of electric plasma oscillators. It is common industry knowledge that a great need for enhanced sub-surface resource production exists. There follows a commensurate opportunity to provide a high energy pulsed plasma emitter oscillator apparatus and methods of use that can generate economically significant resource formation modifications and resource mobilization. Therefore, what is needed is a high energy pulsed plasma emitter system that can cost effectively generate a range of near and far field formation modifications and formation fluid effects that promote rapid resource mobilization and high volume ultimate resource production.